Hemeproteins are an integral part of the respiratory sequence of all aerobic organisms. Despite their importance and ubiquitous nature, the redox chemistry of these units remains largely undefined. Indeed a parallel knowledge of the reduction and oxidation of the "prosthetic group" of these entities, iron porphyrins, by organic and inorganic molecules is only beginning to emerge. The objective of this proposal is to discern the scope and mechanism of the oxidation and reduction of hemeproteins by certain organic and inorganic molecules and free radicals. It is a parallel to our work with iron porphyrins. In the long run it is intended to sort out those characteristics of scope and mechanism imparted by the respective apoenzymes of a hemeprotein that render the redox properties of a heme in its native protein matrix different from that of defined metalloporphyrin complexes in solution. This endeavor is a most important part of a broad effort in the author's laboratory aimed at (1) formulating the biochemical reactions of hemoproteins in molecular terms; (2) employing biochemical catalysts for organic synthesis; (3) determining the mode of intoxication of organisms by alkyl halide biocides and other environmental contaminants.